The field of the invention pertains to centrifuge devices and methods. The invention relates more particularly to a centrifuge tube which utilizes a funnel-shaped divider insert for collecting and dispensing mixed, concentrated fluid samples, and a method for collecting and dispensing the same.
Medical and other laboratories routinely process and handle various sample test fluids, e.g. urine from a human subject, for microscopic observation and analysis. In many of these procedures, such as urinalysis, the sample test fluid is generally much too diluted to quantitatively or qualitatively observe and analyze the solid particles, bacteria, and other constituents, e.g. blood cells, present in the fluid. Therefore, these particulates and fluid constituents must be accumulated to increase the particulate concentration of the test fluid. This is typically accomplished by subjecting the fluid samples to centrifugal forces in a centrifuge. Centrifugation produces a highly concentrated fluid sample which can facilitate identification of certain particulates and constituents present in the fluid, and which ultimately facilitates analysis of the fluid under a microscope.
In a typical urinalysis procedure, for example, a urine sample is taken from a test subject and placed in a test tube which is then spun in a centrifuge, thereby forcing denser particulate material to the bottom of the tube. Subsequently, most of the supernatant liquid produced is decanted off the top. In one common sample preparation method a pipette having a bulbous portion is then placed into the centrifuge tube and squeezed to agitate, disperse and sample the sedimented particulates and some of the liquid at the bottom of the tube. The concentrated sample is then transferred to a microscope slide for observation and analysis.
In an effort to improve this and other fluid concentrating procedures, various types of devices and methods have been developed whereby the particles and solids in a fluid sample may be collected and concentrated in a relatively small volume of liquid. For example, in U.S. Pat. No. 3,914,985 a centrifuge tube is shown having a closed outer tube and a removable inner tube placed inside the closed outer tube. A capillary tube is held by the removable inner tube. And particulate material is collected in the capillary passage, which is then separated and re-centrifuged at a higher speed to compact the particles within the capillary passage. The centrifuge tube disclosed in the ""985 patent, however, is not designed or intended to remove the compacted particles for observation and study under a microscope. Rather, upon centrifugation, the columns of compacted particles are visually measured by a ruler or other measuring means to obtain a determination of the packed cell volume of the particulates, e.g. red cells.
In U.S. Pat. No. 4,981,654 a unitary centrifuge tube and dispensing receptacle is shown for facilitated dispensing of the collected sediment. After centrifuging the tube, the dispensing receptacle, i.e. the lower part, may be removed by twisting it at a short narrow tube portion which connects the dispensing receptacle to the main tube. Additionally, in U.S. Pat. No. 5,647,990, a two-part centrifuge tube is shown wherein the device has a filter and concentrating pocket in the inner reservoir, and an outer tube for filtrate collection.
Perhaps the greatest problem with the ""654 and ""990 patents, however, is that they do not sufficiently address the problem of adequately mixing the post-centrifuge, sedimented particulates with the liquid portion of the concentrated fluid sample collected. At high centrifuge speeds, sedimented particulates and other solid and semi-solid constituents in the fluid tend to bind and stick along the bottom of the collection reservoir, e.g. the dispensing receptacle of the ""654 patent, which must be loosened and mixed prior to dispensation. This can be an arduous and difficult task, especially when air or other gaseous elements are not present to facilitate turbulent mixing. The advantage of producing an air pocket is that it provides a countervailing medium having a lesser density which enables intra-volume turbulent agitation and mixing of the post-centrifuge, concentrated fluid sample. Mixing of the centrifuged and collected fluid concentrate is an essential step in such concentration procedures because inadvertent retrieval and study of only the supernatant liquid portion of the centrifuged and concentrated, but unmixed, fluid sample would yield greatly inaccurate and misleading results.
It is therefore an object of the present invention to provide a simple and efficient device and method for collecting and dispensing mixed concentrated fluid samples.
It is a further object of the present invention to provide a centrifuge tube having means for producing an air pocket for use in mixing the concentrated fluid sample collected subsequent to undergoing a centrifuge process.
It is a still further object of the present invention to provide a cost-effective centrifuge tube having a minimal number of components and capable of being mass-produced by conventional manufacturing methods.
It is a still further object of the present invention to provide a method for collecting and dispensing a mixed concentrated fluid sample utilizing the aforementioned centrifuge tube.
The present invention is for a centrifuge tube for collecting and dispensing a concentrated fluid sample. The centrifuge tube comprises an elongated tube body surrounding a tube volume and has an open top end and a bottom end having a discharge opening. Preferably the discharge opening is located at a tip of a discharge spout extending from the bottom end of the elongated tube body. The centrifuge tube also comprises discharge-opening occluding means, which is adapted to be disengaged from a discharge-opening closed position to a discharge-opening open position. Preferably, the centrifuge tube also comprises a top occluding means which is preferably a tube cap hinged to the open top end, and which is movable between a top open position and a top closed position occluding the open top end. And finally, the centrifuge tube has means for dividing the tube volume into an upper chamber which is adjacent the open top end, and a lower chamber which is adjacent the bottom end. The means for dividing is preferably a divider insert and has a passageway which communicates between the upper and lower chambers. The passageway has a lower terminus positioned in the lower chamber above the bottom end of the elongated tube body.
Additionally, the present invention is for a method for collecting and dispensing concentrated fluid samples which utilizes the centrifuge tube described above. The method comprises the steps of (1) providing the centrifuge tube as described above, (2) in the closed positions of the discharge opening and the open top end, filling the upper chamber with a fluid through the open top end, (3) occluding the open top end with the top occluding means, (4) subjecting the centrifuge tube to centrifugal forces in a centrifuge, such that a concentrated fluid sample is collected in the lower chamber and an air pocket is captured between the lower terminus of the passageway and the means for dividing the tube volume, (5) agitating the lower chamber to mix any centrifuged material into any liquid in the lower chamber, thereby forming a mixed concentrated fluid sample, (6) removing the discharge-opening occluding means from the discharge opening to the discharge-opening open position, and (7) dispensing the mixed concentrated fluid sample through the discharge opening.